I visited the shop to get those components that were mentioned of before and they were unavailable in the shop. So I ordered them from different countries. The good news is the circuit is working fine now without getting hot. I have maintained the original circuit but what I did was I have modified the circuit by changing the 24v supply to 17v and the tip122 stop getting hot. The problem is resolved now, but can you please tell me why it's resolve or is it because of the volt that was changed from 24v to 17v